1. Field of the Invention
The invention relates generally to handheld sensor devices, such as stud sensors, and more specifically to projection of visual indicators against a surface regarding a hidden object.
2. Background of the Invention
Portable sensors, including handheld detector units, are used to locate hidden objects are known. For example, U.S. Pat. Nos. 4,099,118, 4,464,622, and 6,259,241, which are incorporated herein by reference, disclose detector units (e.g., “stud sensors” and alternating current detectors) that identify a hidden object's position behind a surface. Some handheld detectors identify the hidden object by measuring a capacitance change in one or more sensor elements within the detector unit as the user moves the unit across the wall over the hidden object. Such hidden objects include wooden structural studs, pipes, and other metal and nonmetal objects such as wiring. Some handheld detectors contain sensor element and detecting circuitry to measure electromagnetic field changes to identify wires carrying alternating current. Some detectors identify objects that affect a local magnetic field, such as masses of metal or gas lines.
FIG. 1 illustrates a typical application in which a user holds a handheld sensor device 10 against wall or other surface 12. The user moves device 10 transversely, as indicated by the arrows, to detect an object hidden from view behind the surface 12. The object may be hidden framing or a stud 14 defining a first edge 18, a centerline 20 and a second edge 22. Circuits within device 10 display the sensed information on display 16.
A handheld detector unit typically indicates a sensed feature (e.g., an edge 18 or a centerline 20) using a visual display, such as display 16. A device's visual display may include one or more light-emitting diodes (LEDs) and/or liquid crystal display (LCD) in various configurations. For example, some devices include an arrow-shaped LED display. Another device sold under the name Intellisensor® made by Stanley in New Britain, Conn., uses a vertical line of LEDs for a display. In addition, U.S. Pat. No. 6,249,113, issued Jun. 19, 2001, and U.S. Pat. No. 5,917,314, issued Jun. 29, 1999, both incorporated herein by reference, disclose several LCD and LED display configurations. Typically, a visual display 16 of a handheld sensor device is designed to assist the device user in determining some characteristic of a sensed object, such as an edge or a centerline. Referring again to FIG. 1, for example, display 16 may indicate stud 14′s edge 18, a centerline 20 located between edge 18 and edge 22, both edges 18 and 22, or other representations of stud 14.
The display or displays 16 are typically mounted in the housing of the handheld sensor device. Thus, the display 16 is distance from the surface 12. That is, the display 16 is displaced both laterally and in depth from the surface 12 behind which the detected object is located. Furthermore, users often operate handheld detectors at skewed angles and in unusual positions such as when searching for objects that are behind ceilings, floors, corners, etc. For example, in FIG. 1, if stud 14 is located behind a surface 12 that is close to a large visual obstruction, such as a water heater tank, the user will have difficulty seeing display 16. Even if display 16 is visible, the skewed viewing angle requires the user to make a visual angular estimate of the hidden object's location behind the surface, based on the display's position in the detector unit housing.
Known in an unrelated art is projecting information from a computer against a surface. For example, U.S. Pat. No. 6,266,048, by Carau, Sr., issued on Jul. 24, 2001 and titled “Method and apparatus for a virtual display/keyboard for a PDA”, discloses a computer or PDA with a projected display onto a substantially flat, white surface to create a virtual computer screen display and a projected keyboard onto the substantially flat, white surface. Similarly in U.S. Pat. No. 7,215,327, by Liu et al. issued May 8, 2007 and titled “Device and method for generating a virtual keyboard/display”, a keyboard and display are projected. Such projection technologies may be advantageously used in handheld sensor devices.
Handheld sensor devices, such as stud sensors, wall scanners, AC voltage detectors and magnetic field disturbance sensors, display information to a user using one or more LEDs and/or LCD displays located on the body of the device. Some devices use light passed through an aperture or slit on the body of the device to project a line or lines onto the wall surface. Such a slit does not produce a distinct two-dimensional icon but rather a length of light that has no discernible or distinctive features along a dimension. See, for example, U.S. Pat. No. 6,259,241, by Krantz issued on Jul. 10, 2001 and titled “Projected display for portable sensor indicating the location of a detected hidden object behind a surface”, which discloses a handheld detector that projects a visible pattern onto the surface behind which a detected object is located. The projected pattern represents one or more predetermined characteristics of the detected object. A predetermined characteristic may include an edge, a position between two edges, a centerline between two edges, a characteristic of the object's mass, and/or an electromagnetic characteristic emitted or affected by the object. Also discloses is a narrow aperture defined in one end of the detector unit housing. When the detector unit's sensing circuit detects a hidden object, the sensing circuit signals an activating circuit that energizes a light source within the detector housing. A portion of the light from the light source passes through the aperture and thereby projects a line onto the surface beneath which the detected object is located. The line is projected in a single dimension. That is, there is no lateral distinctiveness to the projected line. Furthermore, the projected line may not have distinct side edges or the line may easily be misaligned due to the LED being butted against the aperture opening.
FIG. 1 illustrates a typical application in which a user holds a handheld sensor device against wall or other surface. The handheld sensor device is being used to scan the wall to determine the existence of hidden object beneath the surface. The handheld sensor device may project information various detected features. Such features may include whether the device is over an object (such as a stud), at an edge of the object, or at the center of the object, whether the object is metal, and whether the device is over electrically hot AC wires, etc. Additionally, the device may display a direction to the hidden object. Furthermore, different colors may be projected to help convey changing information to the user. Embodiments project this information using one or more static and/or dynamic apertures.
In general, a conventional handheld sensor device uses visual and audio feedback emanating from device to tell a user of the device that it has detected a stud or other hidden object. Typically, a handheld sensor device includes one or more LEDs and/or an LCD display to visually show the existence of a stud detected behind a wall or other surface. In some devices, a single line or a plurality of lines, and may be projected in one or more directions. Therefore, what is desired is a way to improve how information is presented to the user.